This invention relates to a circuit assembly having an integral frame and a method of making the circuit assembly.
In the prior art, a circuit assembly may be formed of a substrate that is encapsulated with an encapsulation layer to protect the substrate and circuit features from dust, dirt, debris, or unwanted electrical contact. For example, an injection molding process may be used to cover a flexible substrate with a protective encapsulation layer. The substrate may be aligned with respect to the mold sections of the injection molding apparatus to properly register the encapsulation layer with a substrate. However, if a substrate is relatively flexible and has low rigidity, the mechanical stress introduced by a molding operation may deform the substrate during molding. The deformation of the substrate may occur between pins or other hold-down devices associated with the substrate. Accordingly, the circuit assembly may perform unreliably because of circuit irregularities, including electrical shorts, electrical open circuits, or other deficiencies associated with deformation of the substrate of the circuit assembly. Even if the number of pins or hold-down devices per unit area of the substrate is increased to reduce warpage or buckling of the substrate during the encapsulation, localized buckling of the substrate may still occur. Moreover, the greater number of pins or hold-down devices may reduce the circuit density of the substrate by occupying space that could otherwise be used for circuit features. Hold-down pins may expose the substrate in a manner that makes the substrate more prone to damage from the external environment. Thus, the need exists for a circuit assembly that provides structural support to the substrate during the molding process to reduce or eliminate warpage of the substrate. Further, a need exists for protecting the circuit assembly from the deleterious of unwanted debris, dirt, conductive particles, and unwanted electrical contact.
In accordance with the invention, a method for making a circuit assembly facilitates the formation of a reliable circuit assembly that preserves the planarity of a substrate. A substrate is provided comprising one or more conductors. An integral frame of frame elements is formed about the substrate to provide structural support to the substrate. The frame elements are spaced apart to expose intervening regions of the substrate between adjacent frame elements. A dielectric layer is constructed over the intervening regions as a protective barrier for at least one of the conductors, a component, and a circuit feature of the substrate.